Seafood and fish products are important for their nutritional value and also as item of international trade and foreign exchange earnings for a number of countries in the world. Unlike other animal products, the quality of seafood and fish products are more difficult to control due to their variations in species, sex, age, habitats and the action of their autolytic enzymes (Venugopal, 2002). The levels of histamine have been suggested as rapid seafood and fish products spoilage indicators (Male et al., 1996; Tombelli and Mascini, 1998; Patange et al., 2005). Histamine was observed to accumulate in seafood and fish tissues when bacteria spoilage commenced during storage of the products (Male et al., 1996) without altering the seafood and fish normal appearance and odor (Lehane and Olley, 2000). Therefore, simple and rapid techniques for determining the levels of histamine in seafood and fish products are in great demand by the food industry in order to estimate the products freshness.
Histamine exerts its effects by binding to receptors on cellular membranes in the respiratory, cardiovascular, gastrointestinal and haematological immunological system and the skin in the course of allergic and causes reactions such as hypotension, flushing, diarrhea, vomiting and headache (Lehane and Olley, 2000). The symptoms may vary between individuals exposed to the same dose of histamine in contaminated seafood and fish products (Bremer et al., 2003). The US FDA international food safety regulation has quoted 500 ppm as the hazardous level of histamine (FDA, 2001). However, histamine is generally not uniformly distributed in a decomposed fish (Lehane and Olley, 2000; FDA, 2001). Therefore, guidance level of 50 ppm has been set as the chemical index for seafood and fish spoilage. If 50 ppm of histamine is found in one section of the seafood or fish tissues, there is the possibility that other sections may exceed 500 ppm (Lehane and Olley, 2000; FDA, 2001). The seafood and fish products with histamine above that level are prohibited from being sold for human consumption (Gigirey et al., 1998).
Several methods have been proposed for histamine detection such as the routine chromatography analysis, which includes gas chromatography, thin layer liquid chromatography, reversed phase liquid chromatography, liquid chromatography with pre-column, post-column or on-column derivatisation technique and high pressure liquid chromatography (Chemnitius and Bilitewski, 1996; Male et al., 1996; Scott, 1998; Tombelli and Mascini, 1998). However, these methods require complicated and expensive instruments, toxic reagents, time consuming and are not practical for in situ analysis due to the complex sample treatment and requires a trained personnel to carry out such tests.
An amperometric system based on screen-printed electrodes would allow the production of simple, inexpensive and portable devices for rapid seafood and fish product freshness and spoilage determination. Amperometric biosensors measure the electron flow of the oxidation or reduction of an electro-active species. The steady state current is proportional to the concentration of the electro-active species. In the field of enzyme electrodes, the most widely use enzymes are oxidases that produce electro-active hydrogen peroxide, which can be measured by a current signal (Willner et al., 2000) or direct electrochemical communication of a substrate with the enzyme. Amperometric biosensors have been found to overcome most of the other types of biosensor disadvantages. The amperometric biosensors can be operated in turbid media, have comparable instrument sensitivity and are more amenable to miniaturization (Chaubey and Malhotra, 2002).